Compatibilized polymeric compositions comprising polyolefin-polylactic acid copolymers and methods of making the same

ABSTRACT

Polymeric compositions and processes of forming the same are described herein. The processes generally include contacting a polyolefin with a polylactic acid in the presence of at least 800 ppm of radical initiator under extrusion conditions to produce a polyolefin-polylactic acid copolymer.

FIELD

Embodiments of the present invention generally relate to polymericcompositions comprising a biopolymer.

BACKGROUND

Synthetic polymeric materials, such as polypropylene and polyethyleneresins, are widely used in the manufacturing of a variety of end-usearticles ranging from medical devices to food containers. White articlesconstructed from synthetic polymeric materials have widespread utility,these materials tend to degrade slowly, if at all, in a naturalenvironment. In response to environmental concerns, interest in theproduction and utility of more readily biodegradable polymeric materialscomprising polylactic acid, a biodegradable polymer, has beenincreasing. These polymeric materials, also known as “green materials”,may undergo accelerated degradation in a natural environment.

However the utility of polymeric compositions comprising polylacticacid, such as blends of polyolefin and polylactic acid, is often limitedby their poor mechanical and/or physical properties due, in part, to theinherent immiscibility of polyolefin and polylactic acid. To increasethe adhesion between the polyolefin and the polylactic acid, acompatibilizing agent, also referred to herein as a compatibilizer, maybe added to the blend to enhance adhesion at the interface between thepolyolefin and polylactic acid molecules. However, the addition of acompatibilizing agent may have environmental drawbacks such as requiringthe handling of toxic chemicals and the outgassing of volatiles not onlydialog production but also from the end-use products or articles.Moreover, the addition of a compatibilizer increases the cost offormulating the polymeric materials. Thus, a need exists for polymericcompositions comprising polylactic acid that may be compatibilized insitu, without a need to add a compatibilizing agent additive as istypically required in formulating conventional polymeric compositionscomprising polylactic acid.

SUMMARY

Embodiments of the present invention include processes for forming apolymeric composition. The processes generally include contacting apolyolefin with a polylactic acid in the presence of at least 800 ppm ofa radical initiator under extrusion conditions to produce apolyolefin-polylactic acid copolymer.

One or more embodiments include the process of the preceding paragraph,wherein the radical initiator is selected to improve adhesion of thepolyolefin and the polylactic acid over a blend of the polyolefin andpolylactic acid absent the radical initiator.

One or more embodiments include the process of any preceding paragraph,wherein the polyolefin is selected from polypropylene, polyethylene,copolymers thereof and combinations thereof.

One or more embodiments include the process of any preceding paragraph,wherein the copolymer includes from about 30 wt. % to about 70 wt. %polyolefin.

One or more embodiments include the process of any preceding paragraph,wherein the polylactic acid is selected from poly-(D-lactide),poly(L-lactide), and combinations thereof.

One or more embodiments include the process of any preceding paragraph,wherein the copolymer includes from about 30 wt. % to about 70 wt. %polylactic acid.

One or more embodiments include the process of any preceding paragraph,wherein the radical initiator is a peroxide.

One or more embodiments include the process of any preceding paragraph,wherein the peroxide is selected born2,5-dimethyl-2,5-di-(tert-butylperoxy) hexane,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, dicumyl peroxide,peroxydicarbonate, and combinations thereof.

One or more embodiments include the process of any preceding paragraph,wherein the peroxide contacts the polyolefin and polylactic acid in anamount of from about 800 ppm to about 20,000 ppm.

One or more embodiments include the process of any preceding paragraph,wherein the process further includes contacting the polyolefin thepolylactic acid or combinations thereof with a multifunctional monomer.

One or more embodiments include the process of any preceding paragraph,wherein the contact comprises melt blending the polyolefin with thepolylactic acid in the presence of excess peroxides using a reactiveextrusion process.

One or more embodiments include the process of any preceding paragraphfurther including combining the copolymer with a second polyolefin and apolyester to form a second polymeric blend.

One or more embodiments include the process of any preceding paragraphfurther including forming a multilayer film comprising a polyolefinlayer, a polyester layer and a tie layer disposed between the polyolefinlayer and the polyester layer, wherein the tie layer includes thecopolymer.

One or more embodiments include a polymeric composition obtained by aprocess including contacting a polyolefin with a polylactic acid in thepresence of at least 800 ppm of a peroxide to produce apolyolefin-polylactic acid copolymer.

One or more embodiments include the polymeric composition of thepreceding paragraph, wherein the polyolefin is selected frompolypropylene, polyethylene, copolymers thereof and combinationsthereof.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the polyolefin is selected frompolypropylene homopolymer, polypropylene-based random copolymer, andpolypropylene heterophasic copolymer, and combinations thereof.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the copolymer includes from about 30 wt. %to about 70 wt. % polyolefin.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the polylactic acid is selected frompoly(D-lactide), poly(L-lactide), and combinations thereof.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the copolymer includes from about 30 wt. %to about 70 wt. % polylactic acid.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the radical initiator is a peroxide.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the peroxide is selected from2,5-dimethyl-2,5-di-(tert-butylperoxy) hexane,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, dicumyl peroxide,peroxydicarbonate, and combinations thereof.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the peroxide contacts the polyolefin andpolylactic acid in an amount of from about 800 ppm to about 20,000 ppm.

One or more embodiments include the polymeric composition of anypreceding paragraph further including a multifunctional monomer.

One or more embodiments include a multilayer film including a polyolefinlayer, a polyester layer and a tie layer disposed between the polyolefinlayer and the polyester layer, wherein the tie layer includes thepolymeric composition of any preceding paragraph.

One or more embodiments include the polymeric composition of anypreceding paragraph, wherein the polymeric composition exhibits a Tg ofa PLA phase that is lowered compared to an identical polymericcomposition absent the radical initiator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plot of the DSC melting endotherms as a function oftemperature for the samples 1-4 in Example 1.

FIG. 2 is a plot of the DSC melting endotherms as a function oftemperature for the samples 5-10 in Example 2.

DETAILED DESCRIPTION

A detailed description will now be provided. Each of the appended claimsdefines a separate invention, which for infringement purposes isrecognized as including equivalents to the various elements orlimitations specified in the claims. Depending on the context, allreferences below to the “invention” may in some cases refer to certainspecific embodiments only. In other cases it will be recognized thatreferences to the “invention” will refer to subject matter recited inone or more, hut not necessarily all, of the claims. Each of theinventions will now be described in greater detail below, includingspecific embodiments, versions and examples, but the inventions are notlimited to these embodiments, versions or examples, which are includedto enable a person having ordinary skill in the art to make and use theinventions when the information in this disclosure is combined withavailable information and technology.

Various terms as used herein are defined below. To the extent a termused in a claim is not defined below, it should be given the broadestdefinition skilled persons in the pertinent art have given that term asreflected in printed publications and issued patents at the time offiling. Further, unless otherwise specified, all compounds describedherein may be substituted or unsubstituted and the listing of compoundsincludes derivatives thereof.

Further, various ranges and/or numerical limitations may be expresslystated below. It should be recognized that unless stated otherwise, itis intended that endpoints are to be interchangeable. Further, anyranges include iterative ranges of like magnitude falling within theexpressly stated ranges or limitations.

Compatibilized polymeric compositions including biodegradable polymericcomponents and methods of making and using the same are describedherein. Embodiments of the present invention provide compatibilizedpolymeric compositions comprising a polyolefin-polylactic acid copolymerproduced by combining an olefin based polymer (i.e., polyolefin) and apolylactic acid in the presence of excess peroxides. In one or moreembodiments, the compatibilized polymeric composition comprises apolyolefin, a polylactic acid, and a polyolefin-polylactic acidcopolymer produced in situ by combining the polyolefin and thepolylactic acid in the presence of excess peroxides. In one or moreembodiments, the compatibilized polymeric composition may be formed intoa wide variety of articles such as films, fibers, and hot meltadhesives, for example, by processing the compatibilized polymericcomposition using common polymer processing techniques known to one ofskill in the art. In one or more embodiments, the compatibilizedpolymeric composition, may be used as a compatibilizer for directlycompatibilizing a blend of a second polyolefin and a second polylacticacid (or other polyester) for forming a second compatibilized blend. Inone or more embodiments, the compatibilized polymeric composition may bedisposed as a tie layer between a polyolefin layer and a polylactic acid(or other polyester) layer in order to form a multilayer polymer.

Catalyst Systems

The polyolefins may be formed using any suitable catalyst system usefulfor polymerizing olefin monomers. For example, the catalyst system mayinclude chromium based catalyst systems, single site transition metalcatalyst systems including metallocene catalyst systems, Ziegler-Nattacatalyst systems or combinations thereof, for example. The catalysts maybe activated for subsequent polymerization and may or may not beassociated with a support material, for example. A brief discussion ofsuch catalyst systems is included below, but is in no way intended tolimit the scope of the invention to such catalysts.

For example, Ziegler-Natta catalyst systems are generally formed fromthe combination of a metal component (e.g., a catalyst) with one or moreadditional components, such as a catalyst support, a cocatalyst and/orone or more electron donors, for example.

Metallocene catalysts may be characterized generally as coordinationcompounds incorporating one or more cyclopentadienyl (Cp) groups (whichmay be substituted or unsubstituted, each substitution being the same ordifferent) coordinated with a transition metal through π bonding. Thesubstituent groups on Cp may be linear, branched or cyclic hydrocarbylradicals, for example. The cyclic hydrocarbyl radicals may further formother contiguous ring structures, including indenyl, azulenyl andfluorenyl groups, for example. These contiguous ring structures may alsobe substituted or unsubstituted by hydrocarbyl radicals, such as C₁ toC₂₀hydrocarbyl radicals, for example.

Polymerization Processes

As indicated elsewhere herein, the catalyst systems are used to formolefin-based polymer compositions which are interchangeably referred toherein as polyolefins. Once the catalyst system is prepared, asdescribed above and/or as known to one skilled in the art, a variety ofprocesses may be carried out using the catalyst system to formolefin-based polymers. The equipment, process conditions, reactants,additives and other materials used in polymerization processes will varyin a given process, depending on the desired composition and propertiesof the polymer being formed. Such processes may include solution phase,gas phase, slurry phase, bulk phase, high pressure processes orcombinations thereof, for example, (See, U.S. Pat. Nos. 5,525,768;6,420,580; 6,380,328; 6,359,072; 6,346,586; 6,340,730; 6,339,134;6,300,436; 6,274,684; 6,271,323; 6,248,845; 6,245,868; 6,245,705;6,242,545; 6,211,105; 6,207,606; 6,180,735 and 6,147,173, which areincorporated by reference herein.)

In certain embodiments, the processes described above generally includepolymerizing one or more olefin monomers to form olefin-based polymers.The olefin monomers may include C₂ to C₃₀ olefin monomers, or C₂ to C₁₂olefin monomers (e.g., ethylene, propylene, butene, pentene,4-methyl-1-pentene, hexene, octene and decene), for example. It isfurther contemplated that the monomers may include olefinic unsaturatedmonomers, C₄ to C₁₈diolefins, conjugated or nonconjugateddienes,polyenes, vinyl monomers and cyclic olefins, for example. Non-limitingexamples of other monomers may include norbornene, norbornadiene,isobutylene, isoprene, vinylbenzycyclobutane, styrene, alkyl substitutedstyrene, ethylidenenorbornene, dicyclopentadiene and cyclopentene, forexample. The formed polymer may include homopolymers, copolymers orterpolymers, for example.

Examples of solution processes are described in U.S. Pat. Nos.4,271,060, 5,001,205, 5,236,998 and 5,589,555, which are incorporated byreference herein.

One example of a gas phase polymerization process includes a continuouscycle system, wherein a cycling gas stream (otherwise known as a recyclestream or fluidizing medium) is heated in a reactor by heat ofpolymerization. The heat may he removed from the cycling gas stream inanother part of the cycle by a cooling system external to the reactor.The cycling gas stream containing one or more monomers may becontinuously cycled through a fluidized bed in the presence of acatalyst under reactive conditions. The cycling gas stream is generallywithdrawn from the fluidized bed and recycled back into the reactor.Simultaneously, polymer product may be withdrawn from the reactor andfresh monomer may be added to replace the polymerized monomer. Thereactor pressure in a gas phase process may vary from about 100 psig toabout 500 psig, or from about 200 psig to about 400 psig or from about250 psig to about 350 psig, for example. The reactor temperature in agas phase process may vary from about 30° C. to about 120° C., or fromabout 60° C. to about 115° C., or from about 70° C. to about 110° C. orfrom about 70° C. to about 95° C., for example. (See, for example, U.S.Pat. Nos. 4,543.399; 4,588,790; 5,028,670; 5,317,036; 5,352,749;5,405,922; 5,436,304; 5,456,471; 5,462,999; 5,616,661; 5,627,242;5,666,818; 5,677,375 and 5,668,228, which are incorporated by referenceherein.)

Slurry phase processes generally include forming a suspension of solid,particulate polymer in a liquid polymerization medium, to which monomersand optionally hydrogen, along with catalyst, are added. The suspension(which may include diluents) may be intermittently or continuouslyremoved from the reactor where the volatile components can be separatedfrom the polymer and recycled, optionally after a distillation, to thereactor. The liquefied diluent employed in the polymerization medium mayinclude a C₃ to C₇ alkane (e.g., hexane or isobutane), for example. Themedium employed is generally liquid under the conditions ofpolymerization and relatively inert. A bulk phase process is similar tothat of a slurry process with the exception that the liquid medium isalso the reactant (e.g., monomer) in a bulk phase process. However, aprocess may be a bulk process, a slurry process or a bulk slurryprocess, for example.

In a specific embodiment, a slurry process or a bulk process may becarried out continuously in one or more loop reactors. The catalyst, asslurry or as a dry free flowing powder, may be injected regularly to thereactor loop, which can itself be filled with circulating slurry ofgrowing polymer particles in a diluent, for example. Optionally,hydrogen (or other chain terminating agents, for example) may be addedto the process, such as for molecular weight control of the resultantpolymer. The loop reactor may be maintained at a pressure of from about27 bar to about 50 bar or from about 35 bar to about 45 bar and atemperature of from about 38° C. to about 121° C., for example. Reactionheat may be removed through the loop wall via any suitable method, suchas via a double-jacketed pipe or heat exchanger, for example.

Alternatively, other types of polymerization processes may be used, suchas stirred reactors in series, parallel or combinations thereof, forexample. Upon removal from the reactor, the olefin-based polymer (i.e.,polyolefin) may be passed to a polymer recovery system for furtherprocessing, such as addition of additives and/or extrusion, for example.

Polymer Product

The compatibilized polymeric composition of the present invention maycomprise one or more polyolefins. The polyolefin (and blends thereof)formed via the processes described herein may include, but are notlimited to, linear low density polyethylene, elastomers, plastomers,high density polyethylenes, low density polyethylenes, medium densitypolyethylenes, polypropylene, polypropylene copolymers, copolymersthereof and combinations thereof, for example.

Unless otherwise designated herein, all testing methods are the currentmethods at the time of filing.

In an embodiment, the polyolefin may comprise polypropylene,polyethylene, copolymers thereof or combinations thereof.

In an embodiment, the polyolefin may be a propylene-based polymer. Asused herein, the term “propylene-based” is used interchangeably with theterms “propylene polymer” or “polypropylene” and refers to a polymerhaving at least about 50 wt. %, or at least about 70 wt. %, or at leastabout 75 wt. %, or at least about 80 wt. %, or at least about 85 wt. %or at least about 90 wt % polypropylene relative to the total weight ofpolymer, for example.

In one or more embodiments, the propylene-based polymer may be apolypropylene homopolymer, a polypropylene-based random copolymer, apolypropylene heterophasic copolymer, and combinations thereof.

In an embodiment the propylene-based polymer may have a melting point(T_(m)) (as measured by differential scanning calorimetry) of at leastabout 110° C., or from about 110° C. to about 170° C., or from about115° C. to about 170° C., for example.

The propylene-based polymer may have a melt-mass flow rate (MFR) (asdetermined in accordance with ASTM D-1238 condition “L”) of from about0.01 dg/min to about 1000 dg/min. or from about 0.5 dg/min. to about 30dg/min., or from about 0.5 dg/min. to about 5 dg/min., for example. Inan embodiment, the propylene-based polymer has a low melt flow rate. Asused herein, the term low melt flow rate refers to a polymer having aMFR of less than about 10 dg/min., or in a range from about 0.5 dg/min.to about 10 dg/min., or less than about 6 dg/min., or in a range fromabout 0.5 dg/min. to about 6 dg/min., for example.

In an embodiment, the propylene-based polymer may be a polypropylenehomopolymer. Unless otherwise specified, the term “polypropylenehomopolymer” refers to propylene homopolymers, i.e., polypropylene, orthose polyolefins composed primarily of propylene and may contain up to0.5 wt. % of other comonomers, including but not limited to C₂ to C₈alpha-olefins (e.g., ethylene and 1-butene), wherein the amount ofcomonomer is insufficient to change the amorphous or crystalline natureof the propylene polymer significantly. Despite the potential presenceof small amounts of other comonomers, the polypropylene is generallyreferred to as a polypropylene homopolymer.

In an embodiment, the propylene-based polymer may be apolypropylene-based random copolymer. Unless otherwise specified, theterm “propylene-based random copolymer” refers to those copolymerscomposed primarily of propylene and an amount of at least one comonomer,wherein the polymer includes at least about 0.5 wt. %, or at least about0.8 wt. %, or at least about 2 wt. %, or from about 0.5 wt. % to about5.0 wt. % comonomer relative to the total weight of the copolymer, forexample. The comonomers may be selected from _(c2) to _(c10) alkenes.For example, the comonomers may be selected from ethylene, propylene,1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,4-methyl-1-pentene, and combinations thereof. In one specificembodiment, the comonomer includes ethylene.

In an embodiment, the propylene-based polymer may be a polypropyleneheterophasic copolymer (or impact copolymer). Polypropylene heterophasiccopolymer refers to a semi-crystalline polypropylene or polypropylenecopolymer matrix containing a heterophasic copolymer. The heterophasiccopolymer includes ethylene and higher alpha-olefin polymer such asamorphous ethylene-propylene copolymer, for example. In one example, theheterophasic copolymer may comprise from about 6.0 wt. % to about 12 wt.%. or from about 8.5 wt. % to about 10.5 wt. %, or from about 9.0 wt. %to about 10.0 wt. % ethylene relative to the total weight of thecopolymer.

In an embodiment, the propylene-based polymer may be formed from ametallocene catalyst. In another embodiment, the propylene-based polymeris formed from a Ziegler-Natta catalyst.

In an embodiment, the polyolefin may be an ethylene-based polymer. Asused herein, the term “ethylene based” is used interchangeably with theterms “ethylene polymer” or “polyethylene” and refers to a polymerhaving at least about 50 wt. %, or at least about 70 wt. %, or at leastabout 75 wt. %, or at least about 80 wt. %, or at least about 85 wt. %or at least about 90 wt. % polyethylene relative to the total weight ofpolymer, for example.

The ethylene-based polymer may be a homopolymer or a copolymer, forexample a copolymer of ethylene with one or more alpha-olefin monomerssuch as propylene, butene, hexene, etc.

The ethylene-based polymer may have a density (as measured by ASTMD-792) of from about 0.86 g/cc to about 0.998 g/cc, or from about 0.88g/cc to about 0.908 g/cc, or from about 0.90 g/cc to about 0.998 g/cc orfrom about 0.925 g/cc to about 0.998 g/cc, for example.

In an embodiment, the ethylene-based polymer has a high density. As usedherein, the term “high density polyethylene” refers to ethylene-basedpolymer having a density of greater than about 0.945 g/cc, or in a rangefrom about 0.946 g/cc to about 0.998 g/cc, or greater than about 0.948g/cc, or in a range horn about 0.949 g/cc to about 0.998 g/cc, forexample.

In an embodiment, the ethylene-based polymer may have a melting point(T_(m)) (as measured by differential scanning calorimetry) of at leastabout 120° C., or from about 120° C. to about 140° C., or from about125° C. to about 140° C., for example.

The ethylene-based polymer may have a MFR (as measured in accordancewith ASTM D-1238 condition “E” ) of from about 0.01 dg/min, to about 100dg/min, or from about 0.5 dg/min. to about 30 dg/min., for example. Inan embodiment, the ethylene-based polymer has a low MFR of less thanabout 10 dg/min., or in a range from about 0.5 dg/min. to about 10dg/min., or less than about 6 dg/min., or in a range from about 0.5dg/min. to about 6 dg/min., for example.

In an embodiment, the ethylene-based polymer may be formed from ametallocene catalyst. In another embodiment, the ethylene-based polymeris formed from a Ziegler-Natta catalyst.

The compatibilized polymeric composition may include at least 30 wt. %,or from about 30 wt. % to about 99 wt. %, or from about 30 wt. % toabout 70 wt. %, or from about 35 wt. % to about 65 wt. % polyolefinbased on the total weight of the compatibilized polymeric composition,for example.

The compatibilized polymeric composition further includes polylacticacid. The one or more polyolefins (PO) are contacted with polylacticacid (PLA) in the presence of excess peroxides to form a compatibilizedpolymeric composition (which may also be referred to herein as acompatibilized blend or compatibilized blended material). Such contactmay occur by a variety of methods. For example such contact may includeblending of the polyolefin and the polylactic acid under conditionssuitable for the formation of a blended material. Such blending mayinclude dry blending, melt blending, melt compounding, or combinationsthereof, by known blending techniques such as mixing and extrusion(e.g., twin-screw extrusion), for example.

The polylactic acid may include any polylactic acid capable of blendingwith an olefin-based polymer. For example, the polylactic acid may beselected from poly-L-lactide (PLLA), poly-D-lactide (PDLA),poly-LD-lactide (PDLLA) and combinations thereof. The polylactic acidmay be formed by known methods, such as dehydration condensation oflactic acid (see, U.S. Pat. No. 5,310,865, which is incorporated byreference herein) or synthesis of a cyclic lactide from lactic acidfollowed by ring opening polymerization of the cyclic lactide (see, U.S.Pat. No. 2,758,987, which is incorporated by reference herein), forexample. Such processes may utilize catalysts for polylactic acidformation, such as tin compounds (e.g., tin octylate), titaniumcompounds (e.g., tetraisopropyltitanate), zirconium compounds (e.g.,zirconium isopropoxide), antimony compounds (e.g., antimony trioxide) orcombinations thereof, for example.

In an embodiment, the polylactic acid may have a density of from about1.228 g/cc to about 1.255 g/cc, or from about 1.23 g/cc to about 1.25g/cc or from about 1.235 g/cc to about 1.245 g/cc (as determined inaccordance with ASTM D792), for example.

In an embodiment, the polylactic acid may exhibit a crystalline melttemperature (T_(c)) of from about 140° C. to about 190° C., or fromabout 145° C. to about 185° C. or from about 150° C. to about 180° C.(as determined in accordance with ASTM D3418).

In an embodiment, the polylactic acid may exhibit a glass transitiontemperature (Tg) of from about 45° C. to about 85° C., or from about 50°C. to about 80° C. or from about 50° C. to about 70° C. (as determinedin accordance with ASTM D3417).

In an embodiment, the polylactic acid may exhibit a tensile yieldstrength of from about 4,000 psi to about 25,000 psi, or from about5,000 psi to about 10,000 psi or from about 3,500 psi to about 8,500 psi(as determined in accordance with ASTM D638), for example.

In an embodiment, the polylactic acid may exhibit a tensile elongationof from about 0.5% to about 10%, or from about 1.0% to about 8% or fromabout 1.5% to about 6% (as determined in accordance with ASTM D638), forexample.

In an embodiment, the polylactic acid may exhibit a notched Izod impactof from about 0.1 ft-lb/in to about 0.8 ft-lb/in, or from about 0.2ft-lb/in to about 0.6 ft-lb/in or from about 0.25 ft-lb/in to about 0.5ft-lb/in (as determined in accordance with ASTM D256), for example.

The compatibilized polymeric composition may include from about 1 wt. %to about 70 wt. %, or from about 30 wt. % to about 70 wt. %, or fromabout 35 wt. % to about 65 wt. %, or from about 40 wt. % to about 60 wt.% polylactic acid based on the total weight of the compatibilizedpolymeric composition, for example.

The compatibilized polymeric compositions comprisingpolyolefin-polylactic acid copolymer may he produced by combining thepolyolefin and the polylactic acid blend components in the presence ofan excess of a radical initiator, such as peroxide. To promote couplingreactions between polyolefin and polylactic acid, the polyolefin andpolylactic acid blend components may be initiated in the presence ofexcess peroxide. Examples of peroxides suitable for use in thisdisclosure include without limitation include known peroxides, such asbenzoyl peroxide, tertiary butyl hydroperoxide, ditertiary butylperoxide, hydrogen peroxide, potassium persulfate, methyl cyclohexylperoxide, cumenehydroperoxide, acetyl benzoyl peroxide,tetralinhydroperoxide, phenylcyclohexanehydroperoxide, tertiary butylperacetate, dicumyl peroxide, peroxydicarbonate, petertiary butylperbenzoate, ditertiary amyl perphthalate, ditertiary butyl peradipate,tertiary amyl percarbonate and combinations thereof, for example. In oneor more embodiments, the peroxide includes an organic peroxide. Forexample, the organic peroxides may include2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane which is commerciallyavailable as product Lupersol® 101 from Arkema, Inc.,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane which is commerciallyavailable as product Trigonox® 301 from Akzo Nobel.

In an embodiment, the peroxide may be used (i.e., contact the polyolefinand polylactic acid blend components) in an excessive amount of at leastabout 800 ppm, or in a range from about 800 ppm to about 25,000 ppm orfrom about 2000 ppm to about 20,000 ppm, for example,

The compatibilized polymeric composition may be prepared by contactingthe polyolefin (PO), PLA, and radical initiator under conditionssuitable for the formation of a polymeric blend. For example, suchcontact may include melt blending, melt compounding or combinationsthereof, by known blending techniques such as mixing and extrusion(e.g., twin-screw extrusion), for example. In an embodiment, the blendmay be compatibilized by reactive extrusion of the PO and the PLA in thepresence of an excess of peroxide (e.g., Lupersol 101) using, forexample, a continuous mixer such as a mixer having an intermeshingco-rotating twin screw extruder for mixing and melting the components,to thereby form a compatibilized PO/PLA blend comprisingpolyolefin-polylactic acid copolymer.

The process for forming a compatibilized polymeric composition comprisescontacting a polyolefin with a polylactic acid in the presence of anexcess of a radical initiator, wherein a portion of the polyolefin and aportion of the polylactic acid (i.e., at the interfaces between thepolyolefin phase and the polylactic acid phase) react to produce apolyolefin-polylactic acid copolymer capable of compatibilizing thepolyolefin and the polylactic acid to thereby form a compatibilizedblend. In particular, the polyolefin-polylactic acid copolymer is formedin situ by the radical initiator (i.e., peroxide) acting upon thepolyolefin to generate free radical sites along the polyolefin chainthat may react with a polylactic acid macro-free radical molecule.Polyolefins, such as propylene, ethylene and copolymers thereof, areresponsive to peroxide-generated free radicals. Furthermore, radicalsgenerated by peroxides are also able to abstract hydrogens (e.g.,tertiary hydrogens) on both the polyolefin and the polylactic acidmolecules. Thus, melt blending a polyolefin and polylactic acid in thepresence of relatively excessive peroxide forms certain amounts ofpolyolefin-polylactic acid copolymer at the interfaces between thepolyolefin and polylactic acid phases.

In an embodiment, any of the previously described compatibilizedpolymeric compositions may further comprise additives to impart desiredphysical properties, such as printability, increased gloss, or a reducedblocking tendency. Examples of additives may include, withoutlimitation, stabilizers, ultra-violet screening agents, oxidants,anti-oxidants, anti-static agents, ultraviolet light absorbents, fireretardants, processing oils, mold release agents, coloring agents,pigments/dyes, fillers or combinations thereof, for example. Theseadditives may be included in amounts effective to impart desiredproperties.

Product Application

In an embodiment, the compatibilized polymeric composition comprisingpolyolefin-polylactic acid copolymer may be utilized as a compatibilizerto a second polymeric blend comprising a second polyolefin and apolyester (e.g., polylactic acid) to compatibilize the second blend. Forexample, a compatibilized polymeric composition comprisingpolypropylene-polylactic acid copolymer produced by combiningpolypropylene and polylactic acid in the presence of excess peroxides,may be added to a second polypropylene and polylactic acid blend todirectly compatibilize the second blend. In yet another example, acompatibilized polymeric composition comprising polyethylene-polylacticacid copolymer produced by combining polyethylene and polylactic acid inthe presence of excess peroxides, may be added to a second polyethylene(or polypropylene) and polylactic acid blend to directly compatibilizethe second blend. In another embodiment, the compatibilized polymericcomposition and secondary blends thereof may be formed into a widevariety of articles such as films, dyeable fibers, and hot meltadhesives, for example, by polymer processing techniques known to one ofskill in the art, such as forming operations including film, sheet, pipeand fiber extrusion and co-extrusion as well as blow molding, injectionmolding, rotary molding, and thermoforming, for example. Films includeblown, oriented or cast films formed by extrusion or co-extrusion or bylamination useful as shrink film, cling film, stretch film, sealingfilms, oriented films, snack packaging, heavy duty bags, grocery sacks,baked and frozen food packaging, medical packaging, industrial liners,and membranes, for example, in food-contact and non-food contactapplication. Fibers include slit-films, monofilaments, melt spinning,solution spinning and melt blown fiber operations for use in woven ornon-woven form to make sacks, bags, rope, twine, carpet backing, carpetyarns, filters, diaper fabrics, medical garments and geotextiles, forexample. Extruded articles include medical tubing, wire and cablecoatings, hot melt adhesives, sheets, such as thermoformed sheets(including profiles and plastic corrugated cardboard), geomembranes andpond liners, for example. Molded articles include single andmultilayered constructions in the form of bottles, tanks, large hollowarticles, rigid food containers and toys, for example.

In yet another embodiment, the compatibilized polymeric compositioncomprising polyolefin-polylactic acid copolymer or secondary blends maybe utilized to form a tie layer of a multilayer film. For example, amultilayer film may comprise a polyolefin (PO) layer, a PLA layer forother polyester layer), and a tie layer disposed between the polyolefinlayer and the PLA layer wherein the tie layer comprises thecompatibilized polymeric composition, thereby connecting (tying) thepolyolefin and PLA layers. The multilayer film may be formed by theaddition of the compatibilized polymeric composition to a co-extrusionof the PO and PLA layers.

EXAMPLES

The following examples are given as particular embodiments of thedisclosure and to demonstrate the practice and advantages thereof. It isunderstood that the examples are given by way of illustration and arenot intended to limit the specification or the claims to follow in anymanner.

In a first example, four samples were prepared to evaluatecompatibilized polymeric compositions formed as a function of excessperoxide concentration. For comparison purposes, the first sample(“sample 1”) was prepared by melt blending a propylene homopolymerhaving a 2.8 dg/min. melt flow rate, commercially available as Total3371 (“PP 3371”), with a polylactic acid having a melt index (190° C.2.16 kg) in a range from about 10 dg/min. to about 30 dg/min. (asdetermined in accordance with ASTM D1238), commercially available asNature Works® 3001D (“PLA 3001D”), to form a noncompatibilized blend(“PP 3371/PLA 3001D”) referred to herein as the reference sample. Theconcentrations of the blend components PP 3371 and PLA 3001D were eachabout 50 wt. % based on the total weight of the blend. The second sample(“sample 2”) is a compatibilized polymeric composition produced by meltblending 50 wt. % PP 3371 and 50 wt. % PLA 3001D in the presence of anexcess of a peroxide commercially available as Lupersol® 101, whereinthe peroxide was present in a concentration of about 2000 ppm. The thirdsample (“sample 3”) is another compatibilized polymeric compositionproduced by melt blending 50 wt. % PP 3371 and 50 wt. % PLA 3001D in thepresence of an excess of peroxide Lupersol® 101 having a concentrationof about 5000 ppm. The fourth sample (“sample 4”) is anothercompatibilized polymeric composition produced by melt blending 48 wt. %PP 3371, 50 wt. % PLA 3001D, and 2 wt. % polyethylene glycol (200)diacrylate in the presence of an excess of peroxide Lupersol® 101 havinga concentration of about 2000 ppm. The polyethylene glycol (200)diacrylate is commercially available as product SR-259 (“SR259”) fromSartomer Company, Inc. Each of the blends of samples 1-4 were preparedby melt blending the blend components using a reactive extrusionprocess. Formulations for samples 1-4 are summarized in Table 1.

Differential scanning calorimetry (DSC) was used to investigate theglass transition temperatures of the PLA phases in the blends of samples1-4. FIG. 1 is a plot of the DSC melting endotherms as a function oftemperature during the DSC heating scans of samples 1-4. The glasstransitions temperatures (Tg) obtained from each of the endotherms inFIG. 1 are tabulated in Table 1.

TABLE 1 PP 3371 PLA 3001D SR259 Lupersol ® 101 Sample [wt. %] [wt. %][wt. %] [ppm] Tg [° C.] 1 50 50 — — 58.0 2 50 50 — 2000 56.6 3 50 50 —5000 55.0 4 48 50 2 2000 54.6

The data shows that the use of excessive peroxide during blending of PPand PLA shifts the PLA phase Tg to lower temperatures, as compared tothe reference sample 1 having a Tg of 58.0° C. The PLA phase Tg shiftsof 1.4° C., 3° C., and 3.4° C. for samples 2-4, respectively, toward thelower PP glass transition temperature is the result of enhanced PP-PLAinterphase interactions. In particular, the Tg shifts to lowertemperatures means the PLA molecule motion is affected by the PP phaseswhich have a Tg of about −6° C. This development of interaction betweenthe PP and PLA phases is the in-situ formation ofpolypropylene-polylactic acid copolymers at the interfaces between thetwo phases. A comparison of samples 2 and 3 demonstrates that anincrease in the concentration of peroxide from 2000 ppm to 5000 ppmcauses a greater shift in the PLA phase Tg which indicates a higherconcentration of polypropylene-polylactic acid copolymer in sample 3.Typically, the greater the Tg shift, the more effective thecompatibilization. Thus, increasing the Lupersol® 101 peroxideconcentration in the feed to a concentration of 5000 ppm (or more)increases the in-situ formation of polypropylene-polylactic acidcopolymers. The further downward shift in the PLA phase Tg of sample 4,as compared to samples 2 and 3, demonstrates the most effectivecompatibilization and highest concentration of polypropylene-polylacticacid copolymer may be obtained by the participation of the acrylatemonomer (SR259) to facilitate interlinking between the PP and PLAphases.

In a second example, six samples (samples 5-10) were prepared toevaluate compatibilized polymeric compositions formed as a function ofdifferent peroxides (Lupersol® 101 and Perkadox-24L) and their excessconcentrations. In particular, compatibilization of sample blends formedusing Lupersol® 101 which has two —O—O— groups per molecule is comparedto the compatibilization of sample blends formed using a relativelyweaker peroxide product Perkadox® 24L which has one —O—O— group permolecule. Product Perkadox®24L is a dicetylperoxydicarbonatecommercially available from Akzo Nobel. For comparison purposes, thefifth sample (“sample 5”) was prepared by melt blending propylenehomopolymer Total 3371 (“PP 3371”) with a polylactic acid having a meltindex (190° C., 2.16 kg) in a range from about 30 dg/min. to about 40dg/min. (as determined in accordance with ASTM D1238), commerciallyavailable as NatureWorks® 3251D (“PLA 3251D”), to form anoncompatibilized blend (“PP 3371/PLA 3251D”) referred to herein as thereference sample. The concentrations of the blend components PP 3371 andPLA 3251D were each about 50 wt. % based on the total weight of theblend. The sixth sample (“sample 6”) is a compatibilized polymericcomposition produced by melt blending 50 wt. % PP 3371 and 50 wt. % PLA3251D in the presence of an excess of peroxide Lupersol® 101, whereinthe peroxide was present in a concentration of about 2000 ppm. Theseventh sample (“sample 7”) is another compatibilized polymericcomposition produced by melt blending 50 wt. % PP 3371 and 50 wt. % PLA3251D in the presence of an excess of peroxide Lupersol® 101 having aconcentration of about 5000 ppm. The eighth sample (“sample 8”) isanother compatibilized polymeric composition produced by melt blending50 wt. % PP 3371 and 50 wt. % PLA 3251D in the presence of an excess ofperoxide Perkadox® 24L having a concentration of about 2000 ppm. Theninth sample (“sample 9”) and the tenth sample (“sample 10”) arecompatibilized polymeric compositions produced by melt blending 50 wt. %PP 3371 and 50 wt. % PLA 3251D in the presence of an excess of peroxidePerkadox® 24L having concentrations of about 5000 ppm and 20,000 ppm,respectively. Each of the blends of samples 5-10 were prepared by meltblending the blend components using a reactive extrusion process.Formulations for samples 5-10 are summarized in Table 2.

DSC was used to investigate the glass transition temperatures of the PLAphases in the blends of samples 5-10. FIG. 2 is a plot of the DSCmelting endotherms as a function of temperature during the DSC heatingscans of samples 5-10. The glass transitions temperatures (Tg) obtainedfrom each of the endotherms in FIG. 2 are tabulated in Table 2.

TABLE 2 PLA PP 3371 3251D Lupersol ® 101 Perkadox ® 24L Tg Sample [wt.%] [wt. %] [ppm] [ppm] [° C.] 5 50 50 — — 62.0 6 50 50 2000 — 60.2 7 5050 5000 — 58.0 8 50 50 — 2000 60.8 9 50 50 — 5000 60.7 10 50 50 — 20,00058.3

The data shows that the use of excessive peroxide during blending of thePP and the PLA in samples 6, 7, 8, 9 and 10 shifts the Tg of the PLAphase to lower temperatures (i.e., towards the Tg of the PP phase; Tg ofabout −6° C.) which indicates enhanced interactions between the phasesin these compatibilized PP/PLA blends, as compared to thenoncompatibilized PP/PLA blend of reference sample 5 having a Tg of62.0° C. As previously discussed with respect to Example 1 above, the Tgshifts to lower temperatures indicate that the PLA molecule motion isaffected by the PP phases as a result of in-situ formation ofpolypropylene-polylactic acid copolymers at the interfaces between thetwo phases. The PLA phase Tg shifts of 1.8° C. and 4.0° C. for samples 6and 7, respectively, demonstrates that an increase in the concentrationof Lupersol® 101 peroxide from 2000 ppm to 5000 ppm causes a greatershift in the PLA phase Tg which indicates a higher concentration ofpolypropylene-polylactic acid copolymer in sample 7. As previouslymentioned, generally the greater the Tg shift, the more effective thecompatibilization. Thus, increasing the Lupersol® 101 peroxideconcentration in the feed to a concentration of 5000 ppm (or more)increases the in-situ formation of polypropylene-polylactic acidcopolymers. With regards to samples 8 and 9, the PLA phase Tg shifts of1.2° C. and 1.3° C. for samples 8 and 9, respectively, demonstrate thatan increase in the concentration of Perkadox® 24L peroxide from 2000 ppmto 5000 ppm causes little shift in the PLA phase Tg which indicates thein-situ formation of similarly low concentrations ofpolypropylene-polylactic acid copolymer in both samples 8 and 9. Whereasthe larger PLA phase Tg shift of 3.7° C. for sample 10, as compared tosamples 8 and 9, demonstrates that a significantly higher concentration(20,000 ppm) of the weaker peroxide Perkadox® 24L is required to achievea greater degree of compatibilization, similar to the effect of the 5000ppm of the stronger peroxide Lupersol® 101 in sample 7.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A process comprising: contacting a polyolefinwith a polylactic acid in the presence of at least 800 ppm of a radicalinitiator under extrusion conditions to produce a polyolefin-polylacticacid copolymer; and forming a multilayer film comprising a polyolefinlayer, a polyester layer and a tie layer disposed between the polyolefinlayer and the polyester layer, wherein the tie layer comprises thepolyolefin-polylactic acid copolymer.
 2. The process of claim 1, whereinthe radical initiator is selected to improve adhesion of the polyolefinand the polylactic acid over a blend of the polyolefin and polylacticacid absent the radical initiator.
 3. The process of claim 1, whereinthe polyolefin is selected from polypropylene, polyethylene, copolymersthereof and combinations thereof.
 4. The process of claim 1, wherein thepolyolefin-polylactic acid copolymer comprises from about 30 wt % toabout 70 wt. % polyolefin.
 5. The process of claim 1, wherein thepolylactic acid is selected from poly(D-lactide), poly(L-lactide), andcombinations thereof.
 6. The process of claim 1, wherein thepolyolefin-polylactic acid copolymer comprises from about 30 wt. % toabout 70 wt. % polylactic acid.
 7. The process of claim 1, wherein theradical initiator is a peroxide.
 8. The process of claim 7, wherein theperoxide is selected from 2,5-dimethyl-2,5-di-(tert-butylperoxy) hexane,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, dicumyl peroxide,peroxydicarbonate, and combinations thereof.
 9. The process of claim 7,wherein the peroxide contacts the polyolefin and polylactic acid in anamount of from about 800 ppm to about 20,000 ppm.
 10. The process ofclaim 1 further comprising contacting the polyolefin, the polylacticacid or combinations thereof with a multifunctional monomer.
 11. Theprocess of claim 1, wherein the contact comprises melt blending thepolyolefin with the polylactic acid in the presence of excess peroxidesusing a reactive extrusion process.
 12. The process of claim 1 whereinthe polyolefin-polylactic acid copolymer is combined with a secondpolyolefin and a polyester.
 13. The process of claim 1, wherein thepolymeric composition comprises a PLA phase with a Tg that is loweredcompared to an identical polymeric composition absent the radicalinitiator.
 14. A multilayer film comprising a polyolefin layer, apolyester layer and a tie layer disposed between the polyolefin layerand the polyester layer, wherein the tie layer comprises a polymericcomposition obtained by a process comprising: contacting a polyolefinwith a polylactic acid in the presence of at least 800 ppm of a radicalinitiator to produce a polyolefin-polylactic acid copolymer.
 15. Themultilayer film of claim 14, wherein the polyolefin is selected frompolypropylene, polyethylene, copolymers thereof and combinationsthereof.
 16. The multilayer film of claim 14, wherein the polyolefin isselected from polypropylene homopolymer, polypropylene-based randomcopolymer, and polypropylene heterophasic copolymer, and combinationsthereof.
 17. The multilayer film of claim 14, wherein thepolyolefin-polylactic acid copolymer comprises from about 30 wt. % toabout 70 wt. % polyolefin.
 18. The multilayer film of claim 14, whereinthe polylactic acid is selected from poly(D-lactide), poly(L-lactide),and combinations thereof.
 19. The multilayer film of claim 14, whereinthe polyolefin-polylactic acid copolymer comprises from about 30 wt. %to about 70 wt. % polylactic acid.
 20. The multilayer film of claim 14,wherein the radical initiator is a peroxide.
 21. The multilayer film ofclaim 20, wherein the peroxide is selected from2,5-dimethyl-2,5-di-(tert-butylperoxy) hexane,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, dicumyl peroxide,peroxydicarbonate, and combinations thereof.
 22. The multilayer film ofclaim 20, wherein the peroxide contacts the polyolefin and polylacticacid in an amount of from about 800 ppm to about 20,000 ppm.
 23. Themultilayer film of claim 14, further comprising a multifunctionalmonomer.